1. Field of the Invention
The present invention relates to adjustable beds used in nursing care and the like, and in particular to improving controls for changing the posture of care recipients and so forth lying on the bed.
2. Related Art
Gatch beds having so-called Gatch mechanisms for performing sitting-up and knee-break actions and so forth by flexing the platform surface of the bed longitudinally are a widely known type of adjustable bed. With a Gatch bed, as disclosed in Japanese Published Patent Application No. 2000-135146, the platform surface is partitioned into an upper-body (i.e. includes upper and lower back) platform and a lower-body (i.e. includes upper and lower legs) platform that are linked together, with the Gatch mechanism being operated by manually or mechanically raising the upper and/or lower-body platforms to a prescribed angle from a reference bed surface (generally, “horizontal bed surface”).
However, with adjustable beds such as the above Gatch bed, usually the motion center of the person (e.g. care recipient) lying on the platform surface when performing a sitting-up or knee-break action does not correspond to the motion center of the bed (i.e. coupled position of the upper and lower body platforms), meaning that a displacement exists in the positional relationship between the motion centers of the bed and the care recipient's body.
If the sitting-up action, for example, is performed to raise the care recipient from a lying down position on the Gatch bed when such a displacement exists, the care recipient's back ends up slipping down relative to the surface of the upper-body platform. Shearing and frictional forces occur between the surface of the upper-body platform and the body because of the body weight at this time being placed on the upper-body platform. The shearing and frictional forces work against one another due to the care recipient's body weight, causing problems such as the following.
In the case of care recipients with motor disabilities, for example, the caregiver has to shift the care recipient to the correct position whenever the Gatch action is performed, because of the care recipient having slipped from the predetermined position on the bed surface. This places a large burden on the caregiver particularly when the sitting-up action is performed, since the caregiver is required to pull the care recipient's body back up from where it has slipped down in relation to the surface of the upper-body platform.
Moreover, with extended use of the bed, the shearing and frictional forces are exerted on the care recipient's body every time a Gatch action is performed, the accumulation of which places a burden on the body.
A similar problem also occurs when the lower-body platform is raised from the horizontal bed position to perform the knee-break action. That is, the care recipient's legs slip down in relation to the surface of the raised platform.
While such problems have led to steps currently being taken to align the Gatch bed's motion center as near as possible to that of the care recipient, the height of the platform surface in the prior art is generally raised when a bed is equipped with a Gatch mechanism, making it difficult to construct low platform beds suited to care recipients.
While Japanese Published Patent Application No. 2000-135146, for example, discloses an adjustable bed as a Gatch bed that includes, as part of a sitting-up mechanism, a parallel link mechanism (parallelogram mechanism) in which one of a pair of horizontal links is fixed to the bed frame, it is necessary, structurally, to maintain a certain length of a perpendicular arm included in the parallel link, in order to allow the sitting-up mechanism to operate in an excellent fashion to raise the upper-body platform to a large angle. However, maintaining the length of this perpendicular arm raises the platform surface by a corresponding amount, making it difficult to structure the disclosed bed as a low platform bed. Because of the difficulties in maintaining safety and operability with beds having a high platform surface, the desire is to structure Gatch beds with as low a platform surface as possible.